Process for preparing heat-sealable, printable polyolefin structures



July 10, 1962 WOLINSKI 3 042,971

L. E PROCESS FOR PREPARING HEAT-SEALABLE, PRINTABLE POLYOLEFIN STRUCTURES Filed May 27, 1959 FIG.!

MELT BLEND POLOLEFIN RESIN I IITH O.I-IO% OF AT LEAST ONE MONO-ETHYLENICALLY UNSATURATEO ALIPHATIC HYDROCARBON HAVINC AT LEAST 8 CARBON ATONS.

2 Sheets-Sheet 1 FIG.2

POLYETI-IYLENE RESIN EXTRUDE AT A TEMPERATURE ABOVE I50C TO FORM STRUCTURE EXTRUDE IN THE NOLTEN STATE TO FORM STRUCTURE OUENCH STRUCTURE AT 25-90C SUBJECT AT LEAST ONE SURFACE OF STRUCTURE TO PRINTABILITY TREATMENT DRY STRUCTURE OUENCH STRUCTURE DRY STRUCTURE DRY COATED STRUCTURE COOL STRUCTURE SUBJECT AT LEAST ONE SURFACE OF STRUCTURE TO PRINTABILITY TREATI IENT INVENTOR LEON E. WOLINSKI y 10, 1962 L. E. WOLINSKI 3,042,971

PROCESS FOR PREPARING HEAT-SEALABLE, PRINTABLE POLYOLEF'IN STRUCTURES Filed May 27, 1959 2 Sheets-Sheet 2 INVEATIOR LEON E. WOLINSKI Bug/ ATTORNEY tinned, tates Patent 3,042,97l Patented July 10, 1952 3,042,971 PROCESS FOR PREPARING HEAT-SEALABLE, PRINTABLE POLYOLEFIN STRUCTURES Leon E. Wolinski, Bulfalo, N.Y., assignor to E. I. du

Pont de Nemours and Company, Wilmington, Del, a

corporation of Delaware Filed May 27, 1959, Ser. No. 816,065 13 Claims. (Cl. 18-475) This invention relates to the manufacture of polyethylene structure and coatings. More particularly it relates to the preparation of polyethylene film suitable for conversion to bags, containers and similar packages.

This application is a continuation-in-part of application Serial No. 592,502 filed June 20, 1956, now Patent No. 2,924,584.

One of the disadvantages of polyethylene film in the packaging field resides in its low adhesiveness to dried ink impressions, polymeric coatings, other substrates such as glass, wood, paper, and thermoplastic films other than polyethylene. The result is that any information imprinted on the surface of the polyethylene film such as instructions, advertising, trademarks or recipes are smeared or rubbed off by the normal abrasion suffered by the film during handling. This shortcoming has been substantially overcome by so-called printability treatments described in U.S. Patents 2,502,841; 2,632,921; 2,648,097; 2,668,134; 2,715,075; 2,715,076; 2,715,077 and several patent applications disclosed hereinafter. However, these treatments in turn have caused another problem. The ability of polyethylene to adhere to itself by the application of pressure and heat, i.e. heat-scalability, necessary in converting the film to packages, although satisfactory prior to the printability treatment, falls below satisfactory levels after treatment.

The object of the present invention is to provide a polyethylene structure, particularly film, having improved properties. Another object is to improve the heat-scalability of polyethylene structures without sacrificing the desir able properties of the polyethylene structures. Another object is to provide polyethylene structures and polyethylene coatings having a high level of adhesiveness to printing inks and the like, that can be easily heat-sealed. A more specific object is to provide a polyethylene composition, which when formed into a structure or used as a coating and subjected to a printability treatment, will provide a printable and heat-sealable structure. Other objects will appear hereinafter.

The objects are accomplished by a structure forme from a polyethylene resin having a weight average molecular weight of 15,000-3,000,000 (normally from 200,000 to 1,500,000) but preferably 200,0003,000,000 and containing a small amount, i.e. at least about 0.1% and preferably not more than about based on the weight of the polyethylene resin, of at least one mono-ethylenically unsaturated hydrocarbon, said hydrocarbon having at least 8 carbon atoms, a softening temperature no greater than the lower temperature of the crystalline melting point range of the polyethylene resin, preferably below 100 C., an average normal boiling point above the optical melting point of the polyethylene resin, preferably above 325 C., and a melt viscosity, at a temperature above 110 C., lower than that of the polyethylene resin. The softening temperature of the hydrocarbon additive, which is the melting point in most cases, is determined by placing a chip of the additive on a highly polished copper block and raising the temperature of the block uniformly. The lowest temperature at which the additive sample leaves a molten trail when moved across the block by applying light pressure with a spatula is the softening temperature.

The nature of the polyethylene resin makes it impossible to define a crystalline melting point. Instead, a crystalline melting point range is observed. This extends from a lower temperature at which crystallites begin to disappear to the so-called optical melting point at which crystallites are no longer detectable.

'Ihe hydrocarbon is preferably blended uniformly into the polyethylene composition prior to extrusion. However, the hydrocarbon may be incorporated into the polyethylene resin at any stage during formation of the polyethylene structure or it may be added to the surface of the polyethylene structure after formation.

The aliphatic hydrocarbons suitable for this invention may be straight or branched aliphatic or cycloaliphatic hydrocarbons. They should contain at least 8 carbon atoms and no more than one ethyleni'c linkage per molecule. In the following table are listed some mono-olefinically unsaturated aliphatic hydrocarbons which lit the requirements of the present invention.

Softening orrn Compound Temperature 1 Boiling Point 1 l-nonene -82 147. 2-nonene -80 150. 3-nonpne -70 146. 2-methy1-1-oetene -78 145. l-dPPPTIP 66 171. l-rlndpomm 40 193. 5-m1decene below -30 188. 1-dodecene- -34 213. 6-dodecene below 25 212. l hexadeoeneun 4 286. l-eicosene 29 151 at 1.5 mm. 1-hp'neionsanp 36 134 at 0.04 mm. l-rlnnn arm 41 176 at 0.6 mm. l-tricosene below 30 above 200 at 15 mm. ll-tricosena 1a 225 at 15 mm. l-triacontene 62 218 at 0.5 mm. 17 -peutatriacontene--- 67 above 825. 1-cye1opentylbutene-2 below 100 157.

. 2-cyclohexylpropene-1 below 100. 158. 1-cyclohexylbutene-2- below 100--- 177.

1 Normal (at 760 mm. of mercury) softening and boiling points are given unless otherwise specified.

The preferred compounds are those containing from 20-35 carbon atoms in a straight chain, i.e. eicosene to pentatriacontenes. Of these compounds the following have proved most useful and hence are particularly preferred: ll-tricosene and l7pentat-riacontene.

This invention provides polyethylene structures which display a marked improvement in heat-scalability as shown by high heat-seal strength. Furthermore, the polyethylene structures are more readily heat-sealed to form seals of substantial strength at lower heat-sealing temperatures than used heretofore. Flow sheets of the process of this invention are presented in FIGURES 1 and 2 of the drawing.

As mentioned previously, the most important application of this invention is to polyethylene structures, particularly film, whose surface adhesion has been improved by a so-called printability treatment. It is believed that this printability treatment roughens or modifies the surface of the polyethylene structure to create thereon microscopic hills not detectable by touch and not visible to the naked eye. A polyethylene film surface is considered to be satisfactorily roughened if the surface of the film contains substantially uniformly distributed hills or mounds, each individual hill or mound having a diameter, as measured parallel to the film surface, of at least 0.05 micron to 1 micron, and usually between 0.05 micron to 0.5 micron. The elevation or height of these hills or mounds relative to the flat areas, i.e., areas which appear to be relatively untreated, is seldom greater than 0.2-0.5 micron, and usually not greater than 0.25 micron. As a general rule, the printability treatments do not carve out areas of the film surface to form depressions therein, but rather form bills or mounds having elevations relative to the'untreated film surface. Besides improving printability (adhesion to printing inks), these treatments tend to improve the adhesive qualities of the surface of polyethylene structures to organic coatings in general. However, as mentioned previously, these treatments reduce the ability of polyethylene to adhere to itself when pressure and heat are applied.

For purposes of this invention, the adhesiveness of the surface of the polyethylene structure may be improved by any of a number of known expedients. These include superficial treatment of the polyethylene structure with chlorine gas described in U.S.'Patent No. 2,502,481 to Henderson; treatment in a saturated solution of sodium dichromate in concentrated sulfuric acid, in US. Patent No. 2,668,134 to Horton. U.S. Patent No. 2,632,921 to 'Kreidl, discloses a process of subjecting the surface of the polyethylene structure to a temperature above about 60 C. while maintaining the underlying parts of the structure at a temperature below about 50 C. Similarly,

U.S. Patent No. 2,648,097 to Kritchever discloses exposing the surface to a gas flame while the opposite surface 'is supported on a cool drum. This technique is shown in FIGURE 3 wherein the film 10 is guided by rolls 11 and 16 over a cooled drum l2. Cooling is accomplished by passing a cooling liquid into the drum 12a: 13 and out at 14. Simultaneous heating of the film is accomplished by the use of the gas burner 15. Other techniques involve treatiugthe surface. with ozone whilemaintaining the structure at temperatures above 150 C.;' that is,

the molten structure immediately after extrusion (in the air gap) may be treated with a gas containing ozone. This process is described and claimed ina copending ape plication, U.S. Serial No. 323,271 filed November 29, 1952 by L. E. Wolinski. This proc'es'sisshown in FIG- URE 4 wherein the film 10 is led into a heated chamber 'U.S. Patent No. 2,715,076 relates to t-reatment'with ozone in the presence of nitrous oxide; U.S. Serial No. 323,274

filed November 29, 1952, now Patent No. 2,805,960, re-

lates to treatment with ozone at a temperature of at least 150 C. followed by quenching the structure in an aqueous a solution containing a halogen or halogen acid; and US.

Serial No. 323,275 filed November 29, 1952, now Patent No. 2,801,446, relates to treatment with ozone at a temperature of at least 150 C. followed by quenching the structure in a bath containing a conditioning agent such as hydrogenperoxide, niuous acid, alkaline hypochlorites, concentrated nitric'acid or mixtures of concentrated nitric acid and concentrated sulphuric acid.

ture above 150 C., with nitrous oxide is described in US. Patent 2,715,077 to L. E. .Wolinski. The adhesiveness of the surface of polyethylene may also be improved by quenching a freshly extruded film in an aqueous bath containing a halogen or a halogen acid as described in copending application U.S. Serial No. 347,391 filed April 7 1953 now Patent No. 2,801,447, by L. E. Wolinski. The

polyethylene structure may be heated with a special conditioning agent such as hydrogen peroxide, concentrated nitric acid, nitrous acid, alkaline. hypochlorites, or mixtin-es of 'concentrated nitric acid and concentrated sul- Serial No. 487,701 filed February 11, 1955 now Patent No. 2,878,519, by L. E. Wolinski. The use of high voltage stress accompanied by corona discharge, as disclosed. in British Patent Nos; 715,914 and 722,875, may also be used. This treatment is illustrated in FIGURE wherein a the film is guided by rolls.1-1 and 16 overa grounded Treating the molten polyethylene structure, maintained at a temperametallic drum 24. One or more high voltage electrodes 25 is disposed in spaced-apart relation around a portion of the drum 24. The film 10, while on the drum, is passed through the ionizing gap between the electrode 25 and the drum 24. Ionization of this gap is accomplished by energizing the winding of an adjustable autotransformer 26. The output of the autotransformer 26 is impressed upon the primary winding 27 of a step-up transformer 28. The secondary of transformer 28 is coupled to a frequency changer 29 to convert the 60-cycle input into high voltage, low current, high frequency energy. This voltage is impressed upon the primary 30 of a high voltage ,air core transformer, such as a Tesla coil 31. The resulting high frequency, high voltage is impressed from the secondary winding 32 of the Tesla coil on the, electrode 25 to raise the potential gradient in the gap between the electrode 25 and the drum 24 above the disruptive electric intensity of air in the gap to produce the corona discharge.

' Surfaces of relatively high-density polyethylene structures phuric acid, as described in copending application U.S.

may be made more adhesive by quenching a freshly formed structure after extruding at a temperature of at least 325 C. as described in US. Serial No. 506,660 filed May 6, 1955, now abandoned, by I. Swerlick.

Specific embodiments of the present invention are pre sented in the following examples, Example 2 representing the best mode contemplated for performingthe invention. In all the examples except examples in Table VI, Bakelite DYNH-3 i polyethylene resin flake was used. This particular resin has its lower temperature of the crystalline melting point range at about C., an optical melting point of 109 C., a density of about 0.92 gram/cc. and a weight average molecular weight of 750,000-1,000,000.

EXAMPLES 1-7 A mixture'of polyethylene resin flake and a percentage as given in Table I, based on the weight of the resin, of the additives was melt blended in a Banbury mixer at a temperature ranging from 180 C. to 200 C. The blend was transferred to a rubber mill where it was milled at C. C. to form a sheet. The sheet Was chipped into flakes and fed to an extrusion apparatus.

The blend wasremelted in the extrusion apparatus and extruded at 285 C. in the form of a film through a six inch air gap' into a Water quench bath maintained at about 30 C-.

During its passagethrough the air gap, the molten polyethylene film underwent a printability treatment. The air gap was enclosed by a treating chamber. An ozone/oxygen mixture, containing about 1.2% ozone by volume, was passed through the chamber to'contact one surface of the polyethylene film as described in US. Serial No. 323,271. The ozone/oxygen mixture passed through the chamber at rates of 049 cu. ft./min.,,0.83 cu. ft./min., and 1.66 cu. ft./min. While the polyethylene film was led through the chamber at about 22 ft.-/min.

The properties of the resulting films, compared to a control film, are given in the following table. Heat-Seal Strength was measured in the following manner. The film samples were first cut into 6" squares. Squares from the same sample were then superimposed and sealed along one edge with a steel bar 3 /2" long and /8 Wide at a temperature of 200C. The seals were performed by using a dwell time of 0.15 second and a pressure of 10 lbs./ sq. in. The heat-seals were made by sealing a surface that had undergone a printability treatment to a surface that had not, in a direction transverse to the direction in which the film was extruded. After heat-sealing, the connected squares were cut into strips 3" long and /2" Wide. The free ends of the heat-seal strips were then pulled apart in a tensile testing apparatus at a rate of 100% per minute. The strength of the heat-seal, expressed in grams/in. of width represents the highest force necessary to pull the strips apart.

Manufactured by Union Carbide and Carbon. Corp.

Printability was determined by applying Excelobrite W-500, an ink manufactured by Bensing Brothers & Deeney, to the surface of the film by a commercial ink spreader. The spreader was composed of a steel rod hav- 6 ing table. Heat-seal strength was measured by sealing at the temperatures indicated in the table.

Table III ing fine wires wrapped around it and produced a plurality 5 A Y of fine White lines on the surface of the film. The ink HETSEAL E Q EQ POLYETHYL' was dried by exposure for 3 minutes to a temperature of a 60 C. After the mk cooled to room temperature, a strip, Heabsem Strength of pressure-sensltive tape was apphed to the film surface grams/in.) Using Heatand pressed firmly. The strip was then pulled from the 10 Emmnle Percent Additive g$u fg%% %%E surface of the film and examined to determine whether any ink was removed. If ink were removed, the structure 0 C was classified as non-printable.

Control None 425 025 Table I 12 0.2% ll-tricossne 1, 0.4 11- 1, EFFECT or ADDITIVES ON HEAT-SEAL STRENGTHS or 35 3133233: 5 1,23 PRINTABLE PO E YLENE F 0.1% l7-pentatriaconten 774 1, 238 0.8% l7-pentatriacontene 914 1, 248

Heat-Seal Strength (grams/ inch) at Ozone/Oxygen Rate Example Percent Additive 0.49 0.83 1.60 Cubic Cubic Cubic Ft./Min. Ft./Min. FtJMin.

Control None 1,000 1.040 1,040

Z'N PE PPP EXAMPLES 8-11 In these examples printable polyethylene films, all but one containing additives in accordance with the present invention, were prepared in the manner described for E'- amples 1-7. To obtain printability, the ozone/oxygen mixtures were passed through the treating chamber at a rate of 0.83 cu. ft/min. Heat-seal strengths were measured as in the previous examples except for the use of different sealing temperatures as disclosed in Table II.

EXAMPLES 12-16 Blends of polyethylene resin and the additives were prepared and melt extruded in the form of films as described for Examples 1-7. The extruded films passed through a 6 inch air gap into a water quench at C. with no oxygen/ ozone treatment in the air gap. Instead, printability was obtained by conducting the film from the water quench over a grounded steel drum rotating at a circumferential speed of ft./minute. A Tesla coil was held A2" above the drum and discharged 30,000 volts across the width of the polyethylene film in a manner similar to that described in British Patent No. 715,914.

The properties of the resulting printable films compared to a control film that contained no additive but received the electrical discharge treatment, are given in the follow- EXANIPLES 17-18 Blends of polyethylene resin and the additives were prepared and melt extruded in the form of films as described for Examples 1-7. The extruded films passed through a 6 inch air gap into a water quench at 30 C. with no ozone/oxygen treatment in the air gap. Instead, printability was obtained by treating the film at a speed of 100 ft./min. with a propane/air flame at a flame temperature of about 1900 C., the burner being about from the surface of the film. The top surface of the film attained a temperature over 200 C. While the under surface passed over a chromium roll maintained at 2 C. The details of this printability treatment are given in US. Patent No. 2,648,097.

The properties of the resulting printable films, compared to a control film that contained no additive but received the flame treatment, are given in the following table.

Table IV HEAT-SEAL STRENGTH OF PRINTABLE POLYETHYL- ENE FILM:

EXAMPLES 19-23 Polyethylene film was prepared as described for Examples 1-7 from a blend of resins containing 50% by weight Bakelite DYNH3 and 50% Alathon l4 omitting the additives and the ozone/oxygen treatment. The blended resin had a density of 0.917 gram/cc., a weight average molecular weight of between 750,000 and 1,000,000 and a crystalline melting point range from about C. to an optical melting point of 108 C.

The additives were either dissolved in benzene or dispersed in Water as indicated in the table and applied to the film by dipping the film into the solution or dispersion. The coated film was dried in a circulating air oven at about 60 C. Thereafter, the film was subjected to the electrical discharge treatment as described for Examples 12-16 or the flame treatment as described for Examples 17-18, as indicated in the table.

The results are presented in the following table.

1 Manufactured by E. I. du Pont de Nemours and Company.

A polyethylene film was prepared in the manner described for Examples 1-7 omitting the ozone/oxygen treatment; The results for these non-printable films are given in the following table. .The heat-seal strengths of two commercial polyethylene films (Products X and Y),

7 containing no additives of the type disclosed herein, are

also given for comparative purposes.

5 Table VI HEAT-SEAL STRE NGTH' OF NONPRINTABLE POLY- ETHYLENE FILM Heat-Seal Strength (grams/ inch) Using Heat-Seal Temperatures 0f120 0., 145 0.,

Example Percent Additive and 0 0.

120 C. 145 0 160 Control None No' seal. 300 ProductX None 56 Product Y N a 180 24 0.4% ll-tricosene., 748 926 As shown by the examples, the invention is not only useful in preparing heat-scalable, print-able polyethylene packaging film, but is useful in improving the heat-seal strength of polyethylene film in general, and in lowering the temperature required forsatisfa'ctory heat-seals. In the case of printable polyethylene packaging films, the

, addition of the unsaturated aliphatic hydrocarbons. in accordance with the invention serves to recover the heatseal strength lost by the polyethylene film due to the printability treatment. The use of'these special additives also tends to retard the loss of printability and heat-sealability of the polyethylene film with age such as inevitably occurs during storage prior to printing and conversion of film to bags. 7 7

Besides polyethylene film, the invention is applicable to other self-supporting structures such as filaments, rods, tubes, sheets for lamination and to supported polyethylene structures'wherein polyethylene compositions containing the additives are coated on one or both sides of various base films such as cellophane, polyethylene terephthalate, polyvinylide'ne chloride, etc. It is'applicable to polyethylene'structures of normal density (0.91-0.93 gram/ cc.)",and to polyethylene structures of heavy density ('0.940.96 gram/cc); to polyethylene compositions formed. by copoly-merizing polyethylene with minor amounts of propylene, butylene, isobutylene, styrene,

vinyl-acetate and similar vinyl compounds; to polymethylen'e derived from carbon monoxide and hydrogen as in US. Patent No. 2,652,372 to Farlow and Herrick; and to polypropylene, polybutylene and the like.

In forming polyethylene films either containing the special additives or to which the additive is later applied, a melt extrusion process is usually employed. In general, a molding powder or flake of polyethylene is fed continuously into a melt extrusion machine; the molten poly ethylene is continuously extruded. through a slot orifice,

. {3 r then through an air gap vertically downward into a quench bath or onto a'quench roll maintained at a temperature from 25 C; (1., preferably from 30 'C.60 C. Usually, the polyethylene is extruded from a melt maintained at a temperature above 150 C. .Tubing o'r tubular film is usually extruded froni a melt at a temperature within a range of 150 C. 200 C., whereas flat film is extruded at a temperature which may lie anywhere from above 250 C. to the degradation temperature of the polyethylene. -An alternate process of forming polyethylene film which also employs molten polyethylene comprises milling molten polymer on closely spaced calender rolls to form a film which is conducted vertically downward into a quench bath. In either of these general methods of forming polyethylene film, th e space between the point where the molten film leaves the slot orifice or the last calender roll and the point where the molten film enters the quench bath is termed the air gap." During passage through the air gap, the film is usually permitted to pass uninhibited through the atmosphere; and this provides for. some superficial cooling. Generally, the length of the air gap ranges from 2" to as long as 15 in some cases. In some cases as illustrated in Examples l-l l, the film may be subjected to the printability treatment in the air gap. Besides forming polyethylene structures from the molten polymer, polyethylene structures may also be formed from solutions thereof in a'solvent, or from dispersions of the polyethylene in an inert liquid medium such as water. Similarly, the polyethylene coatings may be applied upon other substrates from a melt, solvent "solution or dispersion in a liquid medium.

The amount of additive required lies above about 0.1% and very rarely above 10%. The precise amount will depend upon the increase in heat-seal strength desired. in cases where it is desired to recover the heat-seal strength lost :by the printability treatment, the amount of additive will depend on the particular printability treatment and the extent of this treatment. In most cases, not more than about 5% of the additive need be incorporated in or applied to the surface of the polyethylene film to recover the heat-seal strength lostdue to the printability treatment. In any case, the unsaturated aliphatic hydrocarbons should be added to the polyethylene structure or polyethylene coating composition prior to any printability treatment.

The following theory is offered to explain the surpris sealing step, the additive tends to exude to the surface,

thus plasticizing the surface of the polyethylene structure. If added to the surface, the additive also serves to plasticiz'e the surface during the heat-sealing step. Plasticization of the surface, inturn, serves to increase the heat-scalability of the structure. 7 As many widely different embodiments can be made without departing from the spirit and scope of this invention, this invention is not limited except as'defined in the appended claims. I

What is claimed is: p 1. A proc'ess for manufacturing a heat-scalable printable polyethylene structure which comprises the steps of melt blending a polyethylene resin having a weight average molecular weight of 15,000 to 3,000,000 with 0.1%- 10%, based on the weight of said resin, of at least one mono-ethylenically unsaturated aliphatic hydrocarbon, said hydrocarbon having at least 8 carbon atoms, a softening temperature belowthe lower temperature of the crystalline melting range of said resin, an average normal boiling temperature above theop tical melting point of said resin and a melt viscosity below that of the polyethylene resinat a temperature above C. toform a 75 mixture; extruding said mixture at a temperature above 150 C. to form a structure; subjecting at least one surface of said structure to a printability treatment; quenching said structure at a temperature between 25 C.90 C.; drying said structure and cooling said structure.

2. A process for manufacturing a heat-sealable, printable polyethylene film which comprises the steps of melt blending of polyethylene resin having a weight average molecular'weight of 15,000 to 3,000,000 with 0.1%-%, based on the weight of the resin, of at least one monoethylenically unsaturated aliphatic hydrocarbon having at least 8 carbon atoms, said hydrocarbon having a softening temperature below 100 C., an average normal boiling temperature above 325 C. and a melt viscosity at a temperature above 110 C. below that of the polyethylene resin to form a mixture; extruding said mixture at a temperature above 150 C. to form a film; subjecting at least one surface of said film to a printabili-ty treatment; quenching said film at a temperature between 25 C.-90 C.; drying said film and cooling said film.

3. A process as in claim 2 wherein the printability treatment comprises exposing the surface of the film to a gas containing ozone while maintaining the film at a temperature above 150 C.

4. A process as in claim 2 wherein the printability treatment comprises grounding the film while discharging electricity across the surface of the film.

5. A process as in claim 2 wherein the printability treatment comprises subjecting one surface of the film to a temperature above 60 C. while the other surface of the film is maintained at a temperature below 50 C.

6. A process as in claim 2 wherein the monoethylenically unsaturated hydrocarbon has -35 carbon atoms.

7. A process as in claim 2 wherein the monoethylenically unsaturated hydrocarbon is 11tricosene.

8. A process as in claim 2 wherein the monoethyleni-' cally unsaturated hydrocarbon is 17-pentatriacontene.

9. A process as in claim 2 wherein said polyethylene resin has a weight average molecular weight of 200,000 to 3,000,000.

10. A process as in claim 2 wherein said resin is extruded at a temperature above 250 C.

11. A process for manufacturing a heat-scalable, printable polyethylene film which comprises the steps of melting a polyethylene resin having a weight average molecular weight of 15,000 to 3,000,000; extruding said resin at a temperature above 150 C. to form a film; quenching said film at a temperature between C.90 C.; drying said film; coating said film with at least one mono-ethylenically unsaturated aliphatic hydrocarbon having at least 8 carbon atoms in a liquid medium to apply 0.1%10%,

based on the weight of the resin, of the hydrocarbon to the polyethylene film, said hydrocarbon having a softening temperature below C., an average normal boiling temperature above 325 C. and a melt viscosity at a temperature above C. below that of the polyethylene resin; drying said coated film; and subjecting at least one surface of said coated film to a printability treatment.

12. A process for manufacturing a heat-scalable printable polyethylene structure which comprises the steps of melt blending a polyethylene resin having a weight average molecular weight of 15,000 to 3,000,000 with 0.1%- 10%, based on the weight of said resin, of at least one monoethylenically unsaturated aliphatic hydrocarbon, said hydrocarbon having at least 8 carbon atoms, a softening temperature below the lower temperature of the crystalline melting range of said resin, an average normal boiling temperature above the optical melting point of said resin and a melt viscosity below that of the polyethylene resin at a temperature above 110 C. to form a mixture; extruding said mixture at a temperature above C. to form a structure; quenching said structure and subjecting at least one surface of said structure to a printability treatment.

13. A process for manufacturing a heat-scalable, printable polymeric structure which comprises the steps of melt blending a polyolefin resin with 0.1%10%, based on the weight of said resin, of at least one mono-ethylenically unsaturated aliphatic hydrocarbon to form a mixture, said hydrocarbon having at least 8 carbon atoms, a softening temperture below the lower temperature of the crystalline melting range of said resin, an average normal boiling temperature above the optical melting point of said resin and a melt viscosity below that of the resin at a temperature above the lower temperature of the crystalline melting range of said resin; extruding said mixture in the molten state to form a structure; subjecting at least one surface of said structure to a printability treatment; quenching said structure; drying said structure and cooling said structure.

References Cited in the file of this patent UNITED STATES PATENTS 2,632,921 Kreidl Mar. 31, 1953 2,648,097 ,Kritchever Aug. 11, 1953 2,725,374 Mosher Nov. 29, 1955 2,801,446 Walinsky Aug. 6, 1957 2,808,382 Jakaitis Oct. 1, 1957 2,838,437 Busse et al. June 10, 1958 2,863,850 Ragsdale Dec. 9, 1958 FOREIGN PATENTS 156,420 Australia June 21, 1951 715,914 Great Britain Sept. 22, 1954 810,474 Great Britain Mar.18, 1959 

1. A PROCESS FOR MANUFACTURING A HEAT-SEALABLE PRINTABLE POLYETHYLENE STRUCTURE WHICH COMPRISES THE STEPS OF MELT BLENDING A POLYETHYLENE RESIN HAVING A WEIGHT AVERAGE MOLECULAR WEIGHT OF 15,000 TO 3,000,000 WITH 0.1% 10%, BASED ON THE WEIGHT OF SAID RESIN, OF AT LEAST ONE MONO-ETHYLENICALLY UNSATURATED ALIPHATIC HYDROCARBON SAID HYDROCARBON HAVING AT LEAST 8 CARBON ATOMS, A SOFTENING TEMPERATURE BELOW THE LOWER TEMPERATURE OF THE CRYSTALLINE MELTING RANGE OF SAID RESIN, AN AVERAGE NORMAL BOILING TEMPERATURE ABOVE THE OPTICAL MELTING POINT OF SAID RESIN AND A MELT VISCOSITY BELOW THAT OF THE POLYETHYLENE RESIN AT A TEMPERATURE ABOVE 110*C. TO FORM A MIXTURE; EXTRUDING SAID MIXTURE AT A TEMPERATURE ABOVE 15/*C, TO FORM A STRUCTURE; SUBJECTING AT LEAST ONE SURFACE OF SAID STRUCTURE TO A PRINTABILITY TREATMENT; QUENCHING SAID STRUCTURE AT A TEMPERATURE BETWEEN 25*C.-90* C.; DRYING SAID STRUCTURE AND COOLING SAID STRUCTURE. 